Industrial, commercial and health-care facilities often employ systems using a fluid under pressure to perform control or other functions. Where the fluid is a liquid, it is often oil under pressure and such systems are referred to as "hydraulic systems." Where the fluid is a gas, it is often air and systems using pressurized gas are called "pneumatic systems." The invention is adapted for use in a pneumatic system.
Such systems are used to power assembly tools, cylinders, automatic production tools, small hoists and dental and surgical equipment, among many others. One need only walk through a modern facility using powered devices of some sort and one is likely to see pneumatic control valves and systems, both pressure and vacuum, at work.
Such systems are usually powered from a pneumatic supply source, e.g., an air compressor or the like. Since such sources often have very poor pressure regulation, the "working" pressure used in the system is derived from a pressure regulator valve interposed between the source and the system. Such regulators provide an output or working pressure somewhat reduced from that of the pressure source.
And not all systems require the same "constancy" of working pressure. For example, a power assembly tool, e.g., a wheel lug wrench on an automotive assembly line, may work quite well at an actual pressure of, say, between 90-110 p.s.i. as a result of a regulator "set point" pressure of 100 p.s.i. In other words, such tool is not affected by variations in the set point pressure of plus or minus 10% or so.
On the other hand, there are precision systems where the working pressure downstream of the pressure regulator is required to be regulated with extreme accuracy. Medical equipment, respirators and the like are examples of such systems.
Prior art regulators have not been entirely satisfactory for systems requiring very closely regulated working pressure. One disadvantage of some known regulators is that pressure is regulated solely with a conventional diaphragm, main stem and main valve seat. These parts have relatively high mass and tend to behave too sluggishly for use in precision systems.
Other prior art regulators use a constant bleed passage as a way of preventing the working pressure from diminishing or from diminishing too rapidly. However, such passages are often functionally integral with the main valving mechanism and can become clogged with airborne particulates flowing toward or through such valving mechanism. And insofar as is known, prior art regulators have no satisfactory means for preventing (or at least diminishing the effect of) an upward-trending pressure in a closely-regulated working pneumatic line.
An improved regulator having exceptionally low hysteresis and provisions for regulating an upward-trending line pressure as well as a downward-trending line pressure (the former being the usual case in a vacuum system and the latter being the usual case in a pressure system) would be an important advance in the art.
As used herein, the terms "pressure regulator" refers to a regulator which control pressure above and below ambient atmospheric pressure, the latter otherwise being known as a vacuum regulator.